Currently, rebar panels are constructed by wire tying, mechanical couplers, and occasionally by a combination of welding and wire tying. All of these processes are costly because they are labor intensive and time consuming. Further, inherent weaknesses within each method limits the size and shape of panel that can be produced, thereby increasing the steps and thus costs in the overall construction process. As a result, conventional reinforcement steel bars (rebar) assembly methods require more steps with increased costs, resulting in the construction of structurally compromised rebar panels.
Tie wire constructed rebar panels often structurally fail for several reasons. Firstly, the connection resulting from the tying process is subject to human inconsistencies. For example, the tie wire connection is only as strong as the individual person making the tie. Thus, structural inconsistencies often exist in panels where more than one person is constructing a panel, or a single person becomes fatigued while doing so.
Even if tied correctly, tied rebar connections severely limit panel size due to wire strength and overall rebar intersection rigidity. Typically, the panels are assembled and tied with the assembly laid out on the ground near the job site. Upon completion of the tying process, a crane or other machine is used to place the panel in the concrete form. Wire tied panels are often incapable of supporting the panel's weight during their placement, often yielding a displacement of the tied rebar members known as “raking.” As the spacing of the rebar must be made within the tolerances specified by the engineer, the displaced rebar must be retied in its specified location increasing labor costs.
Not too different from the tied rebar panels are panels constructed with mechanical rebar couplers. Here, a great variety of mechanical couplers are applied to intersections of the rebar panel in place of wire ties. The couplers are more time consuming to use than the wire tie method discussed above. Generally, however, a more consistent rebar connection is attained when using the mechanical coupler over the tie wire panel construction technique. Thus, when the mechanical coupling is done properly a more consistent panel construction is achieved. However, panels constructed with mechanical couplers are very costly with regards to the multiple steps required to assemble them and the price of the couplers themselves.
Finally, attempts have been made to produce a welded rebar panel. Historically, these attempts have yielded a sub-standard product. All prior welding techniques have not achieved metallurgical properties meeting the requirements for reinforced concrete. Rebar in concrete is designed to support tensile loads; therefore, welds must not compromise the ability of the steel to support such loading. Consequently, a rebar panel constructed with welds not having appropriate metallurgical properties is not desirable and may increase the likelihood of a structural failure.
The present invention is directed to a system and method for the construction of weld-stabilized rebar panels that overcomes the above-mentioned problems.